One of the major concerns of manufacturers is the discovery of latent defects or flaws which may eventually lead to the failure of a product, component or subcomponent (the terms "product," "component," and "subcomponent," are being used interchangeably throughout the instant application). For this reason, manufacturers have employed various testing procedures that expose a mechanical product, component, or subcomponent to various stresses that would normally be expected to contribute to any number of possible failure modes. Once the failure modes were identified, the manufacturers could then redesign the products in order to reduce or even eliminate the failure modes. Examples of stresses include, without limitation, pressure, ultraviolet radiation, chemical exposure, vibration, temperature (e.g., extreme heat or extreme cold, and rapid changes in temperature), humidity, mechanical cycling (e.g., repeatedly opening and closing a hinged door), and mechanical loading.
Previously, laboratories typically conducted standard testing of mechanical products and components using traditional success based testing. This meant that the goal of the test was to measure the number of products or components that successfully survived a specified number of cycles with a specified stress source level (e.g., vibration, cycle load, temperature, humidity). This testing was generally based on field data and manufacturing/design experience.
Another testing approach was based on the introduction of all the stress sources at service levels to an entire system to provide the final verification test before production. This approach was intended to be a recreation of exact stresses seen on a system during field conditions. For example, an automobile cooling system would receive road vibration, glycol flow, pressure, heat, and ambient conditions just as would be expected to occur during a standard test track durability test.
Another major concern of manufacturers is determining and quantifying the design maturity of their products in order to enable them to make intelligent decisions as to whether certain defects should or should not be addressed. Design maturity is generally defined as a measure of a design's maturity based on the potential for improvement in life span by eliminating failure modes.
Generally, random stresses applied to an immature product design tend to cause the accumulation of stress damage throughout the product at a faster rate as compared to more mature product designs (i.e., product designs that have been redesigned numerous times to eliminate actual and potential failure modes). The faster accumulation of stress damage near the immature product design features tends to result in failures at these particular locations after a relatively short period of time. Continued stress testing causes other less immature features to accumulate stress damage and to eventually also fail. Obviously, a large number of failure modes at a relatively early stage of a product's life span will have negative implications for a manufacturer, such as increased warranty claims and customer dissatisfaction. Manufacturers have resorted to reliability studies to attempt to gather information on how long a particular product or component can be subjected to certain stress levels before failing. However, this does not give the manufacturer any significant information as to precisely what the results and benefits of a successful redesign of that failed product or component would be.
Although redesigns of the particular product design features may eliminate failures, or alternatively, increase the time to failure of those features, there currently is no reliable and quantifiable method for providing the manufacturer with the necessary information to decide whether a redesign of a product design feature will be cost effective, and if so, what will be the benefits of the redesign, for example, in terms of increased feature life span.
Therefore, there is a need for an apparatus which is capable of generating all possible stress patterns in mechanical products and components under varying simultaneous stimuli in order to activate failure modes, and a method for determining and quantifying the design maturity of the mechanical products and components based on the information generated by the activation of the failure modes.
Testing in accordance with the present invention can lead to significant product quality improvements, design cost reductions, production cost reductions, reduced warranty repair expense, increased customer satisfaction, and increased market share.